Lake Superior State University Microanalysis and Spectroscopic Characterization Lab
One of the northernmost universities in the U.S., Lake Superior State University is located just across the river from the Canadian city with the same name. Sault Ste. Marie is at the nexus of Michigan’s Upper Peninsula and the Great Lakes, and is a natural location for the school’s field work in environmental science and biology.
In September 2023, Dr. Stephan Kolomyjec, Assoc. Prof. of Biology, and Dr. Derek Wright, facility coordinator of the Micro Analysis and Spectroscopic Characterization Lab
, hosted an open house to demonstrate the new microscopy capabilities to be used in their studies of freshwater sponges and cannabis plants. They were co-Principal Investigators for the school’s new Scanning Electron Microscope, a JSM-IT200 tungsten SEM, which replaces a vintage SEM from the 1990s.
Investigating Heavy Metals in Cannabis and CBD for Human Consumption
“The new SEM opens up a whole new world of capabilities that will help generate data for papers we were already working on,” said Dr. Wright. Of special urgency for his group is a paper for ASTM that addresses heavy metals in the form of particulate contaminants present in hemp that is intended for CBD production.
He explained that his work with Cannabis is related to metal uptake, foreign matter, and consumer product safety. Hemp intended for production for human consumption as CBD can contain a variety of elemental impurities. Wright says that JEOL’s automated Particle Analysis software (PA3) will be used during investigation with SEM-EDS to provide physical and chemical details about the metal particles. As dry samples, they are imaged at low vacuum.
“Cannabis is sticky and picks up microfibers from the environment,” Wright says. Using the SEM exposes “adhered particulate matter such as soil minerals, air pollution, agricultural additives, microplastics/textile fibers, and materials from harvesting/processing equipment. Consumer exposure potential for some elements was found to be high enough to warrant additional investigation as to the possible health effects and may justify additional oversight from regulators,” the paper states.
“Cannabis is both tolerant of elevated heavy metals in soils, and is an efficient accumulator of several potentially toxic elements such that it is a promising candidate for phytoremediation applications. There remains however, little publicly available data on the elemental composition of cannabis for many elements of interest.”
In addition to the Cannabis plants, Wright’s lab will investigate the largely unregulated elemental composition of non-tobacco rolling papers, looking for heavy metals that potentially present a human health risk, such as the use of certain plastic components and metal-based pigments. His water quality research page
further describes his microplastics work.
Freshwater Sponge Research Updates 90-year-old Data for Michigan
Dr. Kolomyjec’s research program on freshwater sponges enticed him to relocate from Australia. “I have been deeply interested in freshwater sponges ever since I first encountered them in the wild during my PhD field work in northern Queensland Australia on the platypus. I tried a couple times since then to get a project started at my previous institutions, but it wasn't until I was on a tenure track position here that it really got off the ground. I actually intended to do a population genetics study, but in attempting to figure out which species would be a good focus for the study I discovered that the last (and only) state-wide survey of freshwater sponges in Michigan took place about 90 years ago. Considering how much freshwater usage has changed over the last century, I didn't want to rely on data that old. So, I found an undergraduate student that was interested in sponges as well and we set out to re-survey the whole state. We originally thought there would be major species declines but we were pleasantly surprised and have found a diverse assemblage of species across the state.”
Imaging the freshwater sponges with the SEM requires some special techniques. “To identify a freshwater sponge down to the species level requires the microscopic examination of the tiny glass structures that make up their skeletons. These tiny structures are called spicules, and just like diatoms they are made of biogenically deposited silicon dioxide (glass). Each species' specimens are unique. However, light microscopy only gets you so far. There is enough variation in microstructure that SEM becomes necessary to really nail down an ID for some samples. This was my impetus for serving as PI and leading the effort to acquire the NSF funding for the SEM that JEOL recently installed at LSSU. With light microscopy, about 10% of our samples were unresolved to species level ID. Adding in a sequencing-based approach we were able to lower that to about 5%. With the SEM we are hoping to drop that below 1% as well as explore other avenues including correlative analysis at the 'tissue' level utilizing SEM, EDS, and uXRF.
“Isolating the spicules for identification involves the use of boiling nitric acid to aggressively remove any soft tissue from the samples, leaving the clean glass elements behind. The clean spicules are then suspended in water and dropped onto 10mm coverslips which are in turn affixed to SEM stubs and sputter coated with gold. Since sponges are filter feeders and diatoms are single celled algae in a glass test, the diatoms end up in and on the sponge samples. This means that preparing spicules for imaging also prepares nice clean diatoms for imaging. Thus, the diatoms are currently a byproduct of the sponge work. However, as a pretty byproduct I try to get a nice image whenever I see something interesting. I hope to find a student with an interest in diatom biodiversity at some point to look through our samples.”
Environmental and Other Studies
“There are lots of potential applications for the new SEM. All the instructors and researchers are using the same big academic lab. In addition to the cannabis work and freshwater sponges, it will be used for geology and forensics,” says Dr. Wright. Among the many projects and publications the group has been working on is an example of a recent poster on toxic metal emissions from fireworks displays. We look forward to seeing what new directions the team will go with the new microanalysis capabilities.
Effects of firework displays on air quality & metal deposition fluxes